Transmission method, reception method, transmission apparatus, and reception apparatus

ABSTRACT

A transmission method includes generating one or more frames for content transfer using IP (Internet Protocol) packets, and transmitting the one or more generated frames by broadcast. Each of the one or more frames contains a plurality of second transfer units, each of the plurality of second transfer units contains one or more first transfer units, and each of the one or more first transfer units contains at least one of the IP packets. An object IP packet of the IP packets which is stored in a first transfer unit positioned at a head in the one or more frames contains reference clock information that indicates time for reproduction of the content in data structure different from data structure of an MMT (MPEG Media Transport) packet, and header compression processing on the object IP packet is omitted.

BACKGROUND 1. Technical Field

The present disclosure relates to a transmission method and the like fortransmitting the content by using IP (Internet Protocol) packets throughbroadcast.

2. Description of the Related Art

A MMT (MPEG Media Transport) scheme (refer to NPTL 1) is a multiplexingscheme for multiplexing and packetizing content such as video and audioand for transmitting the content through one or more transfer channelssuch as broadcast and broadband. When the MMT scheme is applied tobroadcasting systems, reference clock information of a transmissionapparatus is transmitted to a reception apparatus, and the receptionapparatus generates a system clock in the reception apparatus based onthe reference clock information.

CITATION LIST Non-Patent Literature

-   NPTL 1: Information technology-High efficiency coding and media    delivery in heterogeneous environments-Part 1: MPEG media transport    (MMT), ISO/IEC FDIS 23008-1

SUMMARY

In one general aspect, the techniques disclosed here feature atransmission method including: generating one or more frames for contenttransfer using IP (Internet Protocol) packets; and transmitting the oneor more generated frames by broadcast, wherein each of the one or moreframes contains a plurality of second transfer units, each of theplurality of second transfer units contains one or more first transferunits, each of the one or more first transfer units contains at leastone of the IP packets, an object IP packet of the IP packets containsreference clock information that indicates time for reproduction of thecontent in data structure different from data structure of an MMT (MPEGMedia Transport) packet, the object IP packet being stored in a firsttransfer unit positioned at a head in the one or more frames, and headercompression processing on the object IP packet is omitted.

The transmission method and the like according to one aspect of thepresent disclosure can reduce processes for acquiring the referenceclock information by a reception apparatus.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a protocol stack for performingtransfer using an MMT scheme and an advanced BS (Broadcast Satellite)transfer scheme.

FIG. 2 is a diagram illustrating data structure of a TLV packet;

FIG. 3 is a block diagram illustrating a basic configuration of areception apparatus;

FIG. 4 is a block diagram illustrating a functional configuration of thereception apparatus when reference clock information is stored in anextension field of an MMT packet header;

FIG. 5 is a diagram illustrating an acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the extension field of the MMTpacket header;

FIG. 6 is a block diagram illustrating the functional configuration ofthe reception apparatus when the reference clock information is storedin control information;

FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the control information;

FIG. 8 is a block diagram illustrating the configuration of thereception apparatus when the reference clock information is stored inthe TLV packet;

FIG. 9 is a diagram illustrating an example in which a long-format NTPis stored in the TLV packet;

FIG. 10 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the TLV packet;

FIG. 11 is a diagram illustrating structure in which the reference clockinformation is appended immediately before an IP packet header;

FIG. 12 is a diagram illustrating structure in which the reference clockinformation is appended immediately before the TLV packet;

FIG. 13 is a diagram illustrating structure of a transfer slot;

FIG. 14 is a diagram illustrating structure of a slot header of thetransfer slot;

FIG. 15 is a diagram illustrating an example in which a flag is storedin an undefined area of the slot header;

FIG. 16 is a diagram illustrating structure of TMCC control informationunder a transfer scheme for advanced broadband satellite digitalbroadcast;

FIG. 17 is a diagram illustrating stream classification/relative streaminformation of the TMCC control information;

FIG. 18 is a diagram illustrating an example in which the referenceclock information is stored in an undefined field of the slot header;

FIG. 19 is a block diagram illustrating the functional configuration ofthe reception apparatus when information indicating that the referenceclock information is contained within the slot header is stored in TMCCcontrol information;

FIG. 20 is a diagram illustrating the acquisition flow of the referenceclock information when the information indicating that the referenceclock information is contained in the slot header is stored in the TMCCcontrol information;

FIG. 21 is a diagram illustrating a flow of extracting a bit string at aspecific position from the IP packet or compressed IP packet;

FIG. 22A is a diagram illustrating an example of structure of TMCCextension information;

FIG. 22B is a diagram illustrating an example of a conventionallyproposed bit assignment method when the extension area is used as apayload;

FIG. 23 is a diagram illustrating an example of data structure of anextension area in which an extension classification classified in thisway is used;

FIG. 24A is a diagram illustrating an example of syntax when theextension classification is used;

FIG. 24B is a diagram illustrating another example of syntax when theextension classification is used;

FIG. 25 is a block diagram illustrating a functional configuration of areception apparatus according to a second exemplary embodiment;

FIG. 26 is a diagram illustrating an operation flow of the receptionapparatus according to the second exemplary embodiment;

FIG. 27 is a block diagram illustrating a functional configuration of atransmission apparatus; and

FIG. 28 is a diagram illustrating an operation flow of the transmissionapparatus.

DETAILED DESCRIPTION

(Underlying Knowledge Forming Basis of the Present Disclosure)

The present disclosure relates to a method and apparatus in which areception apparatus receives reference clock information transmittedfrom a transmission apparatus and generates (reproduces) a referenceclock in a hybrid delivery system using an MMT (MPEG Media Transport)scheme which is under standardization by MPEG (Moving Picture ExpertGroup).

The MMT scheme is a multiplexing scheme for multiplexing and packetizingvideo and audio to transmit the video and audio via one or more transferchannels such as broadcast and broadband.

When the MMT scheme is applied to a broadcasting system, the referenceclock of the transmission apparatus is synchronized with an NTP (NetworkTime Protocol) prescribed by IETF RFC (Internet Engineering Task ForceRequest for Comments) 5905, and based on the reference clock, a timestamp such as PTS (Presentation Time Stamp) and DTS (Decode Time Stamp)is added to a medium. Furthermore, the transmission apparatus transmitsthe reference clock information to the reception apparatus, and thereception apparatus generates the reference clock (hereinafter alsoreferred to as a system clock) in the reception apparatus based on thereference clock information.

In the broadcasting system, a 64-bit long-format NTP capable ofindicating absolute time is preferably used as the reference clockinformation. However, although the conventional MMT scheme prescribesstoring a 32-bit short-format NTP in an MMT packet header andtransferring the 32-bit short-format NTP, the conventional MMT schemedoes not prescribe transferring the long-format NTP, and it is difficultfor a receiver apparatus to acquire high-precision reference clockinformation.

In contrast, control information, such as a message, a table, and adescriptor, is defined using the long-format NTP. It is possible toappend the MMT packet header to the control information for transfer. AnMMT packet, which is the control information to which the MMT packetheader is appended, is stored in an IP packet, and is transferredthrough a broadcast transfer channel or a broadband channel.

When the MMT packet is transferred using an advanced BS transfer schemeprescribed by the ARIB standard (STD-B44: transfer scheme for advancedbroadband satellite digital broadcast), after encapsulation of the MMTpacket into the IP packet and encapsulation of the IP packet into a TLV(Type Length Value) packet, the MMT packet is stored in a transfer slotprescribed by the advanced BS transfer scheme.

However, when the transmission apparatus stores the reference clockinformation in an MMT packet layer, in order to obtain the referenceclock information, the reception apparatus extracts the TLV packet fromthe transfer slot, extracts the IP packet from the TLV packet, extractsthe MMT packet from the IP packet, and further extracts the referenceclock information from the header or a payload of the MMT packet.Therefore, the reception apparatus involves many processes for acquiringthe reference clock information, and needs longer time until theacquisition.

Also, processes in layers equal to or higher than an IP layer aresoftware processes. Accordingly, when the reference clock information isstored in the MMT packet, the reference clock information is extractedand reproduced by a software program. Therefore, the reference clockinformation to be acquired may contain jitter, depending on throughputof a CPU, interruption by and priority of other software programs, andthe like.

Therefore, a transmission method according to one aspect of the presentdisclosure includes: generating one or more frames for content transferusing IP (Internet Protocol) packets; and transmitting the one or moregenerated frames by broadcast, wherein each of the one or more framescontains a plurality of second transfer units, each of the plurality ofsecond transfer units contains one or more first transfer units, each ofthe one or more first transfer units contains at least one of the IPpackets, an object IP packet of the IP packets contains reference clockinformation that indicates time for reproduction of the content in datastructure different from data structure of an MMT (MPEG Media Transport)packet, the object IP packet being stored in a first transfer unitpositioned at a head in the one or more frames, and header compressionprocessing on the object IP packet is omitted.

Thus, by containing the reference clock information in the TLV packetpositioned at a head within the transfer slot, the reception apparatuscan specify a position of the reference clock information in advance.Therefore, the reception apparatus can reduce (simplify) processes foracquiring the reference clock information. Here, an example of the firsttransfer unit is a TLV packet, an example of the second transfer unit isa slot, and an example of the transfer frame is a transfer slot.

In addition, by the transmission apparatus prescribing presence ofheader compression of the IP packet, the reception apparatus can specifythe position of the reference clock information in more detail. Suchstructure can also simplify the process by which the reception apparatusacquires the reference clock information.

In addition, the content may be stored in the MMT packet within each ofthe IP packets.

In addition, each of the first transfer units may be a variable-lengthtransfer unit, and each of the second transfer units may be afixed-length transfer unit.

In addition, each of the first transfer units may be a TLV (Type LengthValue) packet, each of the second transfer units may be a slot under thetransfer scheme for advanced broadband satellite digital broadcast, andeach of the frames may be a transfer slot under the transfer scheme foradvanced broadband satellite digital broadcast.

In addition, the reference clock information may be an NTP (Network TimeProtocol).

In addition, the frames may be transmitted in a predeterminedtransmission cycle.

A reception method according to one aspect of the present disclosureincludes: receiving by broadcast one or more frames for content transferusing IP (Internet Protocol) packets, the one or more frames containingreference clock information; extracting the reference clock informationfrom the received frames; and generating a clock for reproducing thecontent by using the extracted reference clock information, wherein eachof the one or more frames contains a plurality of second transfer units,each of the plurality of second transfer units contains one or morefirst transfer units, each of the one or more first transfer unitscontains at least one of the IP packets, an object IP packet of the IPpackets contains the reference clock information that indicates time forreproduction of the content in data structure different from datastructure of an MMT (MPEG Media Transport) packet, the object IP packetbeing stored in a first transfer unit positioned at a head in the one ormore frames, and header compression processing on the object IP packetis omitted.

A transmission apparatus according to one aspect of the presentdisclosure includes: a generator that generates one or more frames forcontent transfer using IP (Internet Protocol) packets; and a transmitterthat transmits the one or more generated frames by broadcast, whereineach of the one or more frames contains a plurality of second transferunits, each of the plurality of second transfer units contains one ormore first transfer units, each of the one or more first transfer unitscontains at least one of the IP packets, an object IP packet of the IPpackets contains reference clock information that indicates time forreproduction of the content in data structure different from datastructure of an MMT (MPEG Media Transport) packet, the object IP packetbeing stored in a first transfer unit positioned at a head in the one ormore frames, and header compression processing on the object IP packetis omitted.

A reception apparatus according to one aspect of the present disclosureincludes: a receiver that receives by broadcast one or more frames forcontent transfer using IP (Internet Protocol) packets, the one or moreframes containing reference clock information; an extractor thatextracts the reference clock information from the received frames; and agenerator that generates a clock for reproducing the content by usingthe extracted reference clock information, wherein each of the one ormore frames contains a plurality of second transfer units, each of theplurality of second transfer units contains one or more first transferunits, each of the one or more first transfer units contains at leastone of the IP packets, an object IP packet of the IP packets containsthe reference clock information that indicates time for reproduction ofthe content in data structure different from data structure of an MMT(MPEG Media Transport) packet, the object IP packet being stored in afirst transfer unit positioned at a head in the one or more frames, andheader compression processing on the object IP packet is omitted.

Note that these comprehensive or specific aspects may be implementedusing a system, an apparatus, a method, an integrated circuit, acomputer program, or a computer-readable recording medium such as aCD-ROM. Also, these comprehensive or specific aspects may be implementedusing any combination of a system, an apparatus, a method, an integratedcircuit, a computer program, and a recording medium.

Exemplary embodiments will be specifically described below withreference to the drawings.

Note that each of the exemplary embodiments below describes acomprehensive or specific example. Numerical values, shapes, materials,elements, arranged positions and connection forms of the elements,steps, the order of the steps, and the like described in the followingexemplary embodiments are merely an example, and do not intend to limitthe present disclosure. Also, among elements described in the followingexemplary embodiments, elements that are not included in an independentclaim which represents the highest concept are described as optionalelements.

First Exemplary Embodiment

[Basic Configuration of an MMT Scheme]

First, a basic configuration of an MMT scheme will be described. FIG. 1illustrates a protocol stack diagram for performing transfer using theMMT scheme and an advanced BS transfer scheme.

Under the MMT scheme, information such as video and audio is stored in aplurality of MPUs (Media Presentation Units) and a plurality of MFUs(Media Fragment Units), and an MMT packet header is added forMMT-packetization.

Meanwhile, under the MMT scheme, the MMT packet header is added tocontrol information such as an MMT message for MMT-packetization. TheMMT packet header is provided with a field that stores a 32-bitshort-format NTP, and this field may be used for QoS control ofcommunication networks, etc.

MMT-packetized data is encapsulated into an IP packet having a UDPheader or IP header. At this time, in the IP header or UDP header, whena set of packets with an identical source IP address, destination IPaddress, source port number, destination port number, and protocolclassification is an IP data flow, headers of the plurality of IPpackets contained in one IP data flow are redundant. Therefore, headercompression of some IP packets is performed in one IP data flow.

Next, a TLV packet will be described in detail. FIG. 2 is a diagramillustrating data structure of the TLV packet.

As illustrated in FIG. 2 , an IPv4 packet, IPv6 packet, compressed IPpacket, NULL packet, and transfer control signal are stored in the TLVpacket. These pieces of information are identified using an 8-bit datatype. Examples of the transfer control signal include an AMT (AddressMap Table) and NIT (Network Information Table). Also, in the TLV packet,a data length (byte unit) is indicated using a 16-bit field, and a valueof data is stored after the data length. Since there is 1-byte headerinformation before the data type (not illustrated in FIG. 2 ), the TLVpacket has a total of 4-byte header area.

The TLV packet is mapped to a transfer slot under the advanced BStransfer scheme. Pointer/slot information that indicates a head positionof a first packet and a tail position of a last packet which arecontained in every slot are stored in TMCC (Transmission andMultiplexing Configuration Control) control information (controlsignal).

Next, a configuration of a reception apparatus when the MMT packet istransferred by using the advanced BS transfer scheme will be described.FIG. 3 is a block diagram illustrating the basic configuration of thereception apparatus. Note that the configuration of the receptionapparatus of FIG. 3 is simplified. More specific configuration will bedescribed later individually according to a manner in which referenceclock information is stored.

Reception apparatus 20 includes receiver 10, decoder 11, TLVdemultiplexer (DEMUX) 12, IP demultiplexer (DEMUX) 13, and MMTdemultiplexer (DEMUX) 14.

Receiver 10 receives transfer channel coded data.

Decoder 11 decodes the transfer channel coded data received by receiver10, applies error correction and the like, and extracts the TMCC controlinformation and TLV data. The TLV data extracted by decoder 11 undergoesDEMUX processing by TLV demultiplexer 12.

The DEMUX process performed by TLV demultiplexer 12 differs according tothe data type. For example, when the data type is a compressed IPpacket, TLV demultiplexer 12 performs processes such as decompressingthe compressed header and passing the header to an IP layer.

IP demultiplexer 13 performs processes such as header analysis of the IPpacket or UDP packet, and extracts the MMT packet from each IP dataflow.

MMT demultiplexer 14 performs a filtering process (MMT packet filtering)based on a packet ID stored in the MMT packet header.

[Method for Storing the Reference Clock Information in the MMT Packet]

Under the MMT scheme described with reference to FIG. 1 to FIG. 3described above, although the 32-bit short-format NTP can be stored inthe MMT packet header and transferred, there exists no method fortransferring a long-format NTP.

Hereinafter, a method for storing the reference clock information in theMMT packet will be described. First, the method for storing thereference clock information within the MMT packet will be described.

When control information that defines a descriptor, a table, or amessage for storing the reference clock information is stored in the MMTpacket, the descriptor indicating the reference clock information and anidentifier indicating the table or message are indicated within thecontrol information. Then, the control information is stored in the MMTpacket by a transmission apparatus.

This allows reception apparatus 20 to identify the reference clockinformation based on the identifier. Note that the reference clockinformation may be stored in the MMT packet by using existingdescriptors (for example, CRI_descriptor( ), etc.).

Next, a method for storing the reference clock information in the MMTpacket header will be described.

For example, there is a method for storing the reference clockinformation by using a header_extension field (hereinafter referred toas an extension field). The extension field becomes effective when anextension_flag of the MMT packet header is set to ‘1’.

An extension field type indicating data classification of data to bestored in the extension field is stored in the extension field.Information indicating that the data is reference clock information (forexample, a 64-bit long-format NTP) is stored in the extension fieldtype. Accordingly, the reference clock information is stored in theextension field.

When the header_extension_flag of the MMT packet header is ‘1’,reception apparatus 20 refers to the extension field of the MMT packet.When the extension field type indicates that the data is the referenceclock information, reception apparatus 20 extracts the reference clockinformation and reproduces a clock.

Note that the reference clock information may be stored in an existingheader field. In addition, when there is an unused field or when thereis a field unnecessary for broadcast, the reference clock informationmay be stored in these fields.

In addition, the reference clock information may be stored by using theexisting field and the extension field together. For example, theexisting 32-bit short-format NTP field and the extension field may beused together.

In order to maintain compatibility with the existing field, of the64-bit long-format NTP, a 32-bit section of the reference clockinformation corresponding to a short-format format may be stored in theexisting field, and remaining 32 bits may be stored in the extensionfield.

Here, the reference clock information is, for example, time when a headbit of the MMT packet in which the reference clock information is storedpasses a predetermined position (for example, when the head bit isoutput from a specific component of a transmission apparatus). However,the reference clock information may be time when a bit of anotherposition passes the predetermined position.

When the reference clock information is stored in the MMT packet as thecontrol information, the MMT packet containing the control informationis transmitted at predetermined transmission intervals.

When the reference clock information is stored in the extension field ofthe MMT packet, the reference clock information is stored in theextension field of a predetermined MMT packet header. Specifically, forexample, at least one or more pieces of the reference clock informationare stored in the header extension fields of the MMT packets atintervals of 100 ms.

Note that, when the reference clock information is stored in the MMTpacket, the packet ID of the MMT packet that stores the reference clockinformation is stored in program information. Reception apparatus 20analyzes the program information and acquires the MMT packet in whichthe reference clock information is stored. At this time, the packet IDof the MMT packet in which the reference clock information is stored maybe prescribed in advance as a fixed value. This allows receptionapparatus 20 to acquire the reference clock information withoutanalyzing the program information.

[Operation Flow when the Reference Clock Information is Stored in theMMT Packet]

Next, an operation flow when the reference clock information is storedin the MMT packet (acquisition flow of the reference clock information)will be described.

First, the following describes the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader. FIG. 4 is a block diagram illustrating a functionalconfiguration of reception apparatus 20 when the reference clockinformation is stored in the extension field of the MMT packet header.FIG. 5 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader.

In FIG. 4 , when the reference clock information is stored in theextension field of the MMT packet header, MMT demultiplexer 14 includesreference clock information extractor 15 (an example of an extractor),and reference clock generator 16 (an example of a generator) is provideddownstream of MMT demultiplexer 14.

In the flow of FIG. 5 , decoder 11 of reception apparatus 20 decodes thetransfer channel coded data received by receiver 10 (S101), and extractsthe TLV packet from the transfer slot (S102).

Next, TLV demultiplexer 12 performs DEMUX on the extracted TLV packet toextract the IP packet (S103). At this time, the header of the compressedIP packet is reproduced.

Next, IP demultiplexer 13 performs DEMUX on the IP packet, acquires thespecified IP data flow, and extracts the MMT packet (S104).

Next, MMT demultiplexer 14 analyzes the header of the MMT packet, anddetermines whether the extension field is used and whether the referenceclock information is in the extension field (S106). When there is noreference clock information in the extension field (No in S106), theprocess ends.

On the other hand, when the determination is made that the referenceclock information is in the extension field (Yes in S106), referenceclock information extractor extracts the reference clock informationfrom the extension field (S107). Then, reference clock generator 16generates the system clock based on the extracted reference clockinformation (S108). The system clock is, in other words, a clock forreproducing content.

Next, the acquisition flow of the reference clock information byreception apparatus 20 when the reference clock information is stored inthe control information will be described. FIG. 6 is a block diagramillustrating the functional configuration of reception apparatus 20 whenthe reference clock information is stored in the control information.FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the control information.

As illustrated in FIG. 6 , when the reference clock information isstored in the control information, reference clock information extractor15 is disposed downstream of MMT demultiplexer 14.

In the flow of FIG. 7 , the processes of step S111 to step S114 areidentical to the flow of step S101 to step S104 described in FIG. 5 .

Subsequently to step S114, MMT demultiplexer 14 acquires the packet IDof the packet containing the reference clock information from theprogram information (S115), and acquires the MMT packet of the packet ID(S116). Subsequently, reference clock information extractor 15 extractsthe reference clock information from the control signal contained in theextracted MMT packet (S117), and reference clock generator 16 generatesthe system clock based on the extracted reference clock information(S118).

[Method for Storing the Reference Clock Information in the TLV Packet]

As described in FIG. 5 and FIG. 7 , when the reference clock informationis stored in the MMT packet, in order to obtain the reference clockinformation by the reception apparatus, reception apparatus 20 extractsthe TLV packet from the transfer slot, and extracts the IP packet fromthe TLV packet.

Furthermore, reception apparatus 20 extracts the MMT packet from the IPpacket, and further extracts the reference clock information from theheader or a payload of the MMT packet. Thus, when the reference clockinformation is stored in the MMT packet, reception apparatus 20 has manyprocesses for acquiring the reference clock information, and longer timeis required until the acquisition, which need to be addressed.

Therefore, a method will be described for implementing a process ofadding a time stamp to a medium, such as video and audio, based on thereference clock, and a process of transferring the medium by using theMMT scheme, and for performing transfer of the reference clockinformation by using a lower layer, lower protocol, or lowermultiplexing scheme than the MMT layer.

First, a method for storing the reference clock information in the TLVpacket for transfer will be described. FIG. 8 is a block diagramillustrating the configuration of reception apparatus 20 when thereference clock information is stored in the TLV packet.

Reception apparatus 20 illustrated in FIG. 8 differs from receptionapparatus 20 of FIG. 4 and FIG. 6 in placement of reference clockinformation extractor 15 and reference clock generator 16. In addition,synchronizer 17 and decoding presenter 18 are also illustrated in FIG. 8.

The TLV packet includes the 8-bit data type, 16-bit data length, and8*N-bit data, as illustrated in aforementioned FIG. 2 . In addition,1-byte header which is not illustrated in FIG. 2 exists before the datatype, as described above. Here, the data type is specificallyprescribed, for example, as 0x01: IPv4 packet, 0x03: header-compressedIP packet, etc.

In order to store new data in the TLV packet, an undefined area of thedata type is used to prescribe the data type. In order to indicate thatthe reference clock information is stored in the TLV packet, the datatype describes that the data is the reference clock information.

Note that the data type may be prescribed for each kind of the referenceclock information. For example, the data types that indicate theshort-format NTP, long-format NTP, and PCR (Program Clock Reference) maybe prescribed individually. FIG. 9 is a diagram illustrating an examplein which the long-format NTP is stored in the TLV packet. Thelong-format NTP is stored in a data field.

Reference clock information extractor 15 analyzes the data type of TLVpacket. When the reference clock information is stored, reference clockinformation extractor 15 analyzes the data length, and extracts thereference clock information from the data field.

Here, when the data length is uniquely determined by the data type,reference clock information extractor 15 may acquire the reference clockinformation without analyzing a data length field. For example, when thedata type indicates a 64-bit long-format NTP, reference clockinformation extractor 15 may extract a section from (4 bytes+1 bit)-thbit to (4 bytes+64 bits)-th bit. Also, reference clock informationextractor 15 may extract a desired bit from 64-bit data.

Next, the operation flow of reception apparatus 20 when the referenceclock information is stored in the TLV packet (acquisition flow of thereference clock information) will be described with reference to FIG. 10. FIG. 10 is a diagram illustrating the acquisition flow of thereference clock information performed by reception apparatus 20 when thereference clock information is stored in the TLV packet.

In the flow of FIG. 10 , first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S121), and extracts the TLV packetfrom the transfer slot (S122).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S123),and determines whether the data type is the reference clock information(S124). When the data type is the reference clock information (Yes inS124), reference clock information extractor 15 extracts the referenceclock information from the data field of the TLV packet (S125). Then,reference clock generator 16 generates the system clock based on thereference clock information (S126). On the other hand, when the datatype is not the reference clock information, (No in S124), theacquisition flow of the reference clock information ends.

In addition, in an unillustrated flow, IP demultiplexer 13 extracts theIP packet according to the data type. Then, the IP DEMUX process and MMTDEMUX process are performed on the extracted IP packet, and the MMTpacket is extracted. Furthermore, synchronizer 17 outputs video data todecoding presenter 18 with timing with which the time stamp of the videodata contained in the extracted MMT packet coincides with the referenceclock generated in step S126. Decoding presenter 18 decodes and presentsthe video data.

In a transmission method described above, a storage place of thereference clock information is indicated in the data type of the TLVpacket, and the reference clock information is stored in the data fieldof the TLV packet. Thus, by the transmission apparatus storing andtransmitting the reference clock information by using a lower layer orlower protocol than the MMT layer, reception apparatus 20 can reduce theprocesses and time until reception apparatus 20 extracts the referenceclock information.

Also, since reception apparatus 20 can extract and reproduce thereference clock information in a lower layer extending over the IPlayers, reception apparatus 20 can extract the reference clockinformation by hardware implementation. This allows reception apparatus20 to reduce more influence of jitter or the like than extracting thereference clock information by software implementation, and to generatehigher-precision reference clock.

Next, other methods for storing the reference clock information will bedescribed.

When the data length is uniquely determined according to the data typein the aforementioned flow of FIG. 10 , the data length field does notneed to be transmitted. Here, when the data length field is nottransmitted, an identifier is stored indicating that the data lengthfield is data that is not transmitted.

Although the reference clock information is stored in the data field ofthe TLV packet according to the description of FIG. 10 , the referenceclock information may be appended immediately before or after the TLVpacket. Also, the reference clock information may be appendedimmediately before or after data to be stored in the TLV packet. Inthese cases, a data type that allows specification of a position wherethe reference clock information is appended is added.

For example, FIG. 11 is a diagram illustrating structure in which thereference clock information is appended immediately before the IP packetheader. In this case, the data type indicates an IP packet withreference clock information. When the data type indicates an IP packetwith reference clock information, reception apparatus 20 (referenceclock information extractor 15) can acquire the reference clockinformation by extracting bits of a previously prescribed predeterminedlength of the reference clock information from a head of the data fieldof the TLV packet.

At this time, the data length may specify the length of data thatincludes the length of the reference clock information, and may specifythe length that does not include the length of the reference clockinformation. When the data length specifies the length of data thatincludes the length of the reference clock information, receptionapparatus 20 (reference clock information extractor 15) acquires data ofa length obtained by subtracting the length of the reference clockinformation from the data length from immediately after the referenceclock information.

When the data length specifies the length of data that does not includethe length of the reference clock information, reception apparatus 20(reference clock information extractor 15) acquires data of the lengthspecified by the data length from immediately after the reference clockinformation.

In addition, FIG. 12 is a diagram illustrating structure in which thereference clock information is appended immediately before the TLVpacket. The data type is a conventional data type. An identifierindicating that the TLV packet is a TLV packet with reference clockinformation is stored, for example, in a slot header of the transferslot or the TMCC control information. FIG. 13 is a diagram illustratingstructure of the transfer slot, and FIG. 14 is a diagram illustratingstructure of the slot header of the transfer slot.

In FIG. 13 , the transfer slot includes a plurality of slots (120 slotsof Slot #1 to Slot #120 in the example of FIG. 13 ). The number of bitscontained in each slot is a fixed bit number uniquely determined basedon a coding rate of error correction, each of the slots has a slotheader and stores one or more TLV packets. Note that, in FIG. 13 , theTLV packet is variable-length.

In FIG. 14 , a position of a head byte of a first TLV packet within theslot indicated with the number of bytes from a slot head except the slotheader is stored in a head TLV instruction field (16 bits) of the slotheader. Remaining 160 bits of the slot header is undefined.

The transfer slot includes 120 slots per frame as described above, and amodulation scheme is assigned to the slots in 5-slot unit. In addition,up to 16 streams can be transferred within one frame.

Note that the plurality of streams included in one transfer slot differfrom one another, for example, in content (or a company that providesthe content) transferred by the streams. In addition, each streamincludes one or more slots, and one slot does not extend over theplurality of streams.

When the identifier indicating that the TLV packet is a TLV packet withreference clock information is stored in the slot header, for example,information that allows specification of a position of the TLV packetwith reference clock information, kind of the reference clockinformation, data length, and the like are stored in a slot obtained byextending (using) an undefined field of the slot header.

Note that all pieces of information including the information thatallows specification of the position of the TLV packet with referenceclock information, kind of the reference clock information, and datalength do not need to be stored in the slot header. The slot only needsto indicate information that allows specification of and reference tothe TLV packet with reference clock information.

For example, when definition is made that the reference clockinformation is a 64-bit long-format NTP, that only one TLV packet withreference clock information can be stored in one slot, and that the oneTLV packet with reference clock information is always a head TLV packet,a flag may be stored in the undefined area of the slot header. FIG. 15is a diagram illustrating an example in which the flag is stored in theundefined area of the slot header.

In FIG. 15 , the flag (described as “F” in the diagram) indicatingwhether the reference clock information is contained in the slot isstored in the undefined area of the slot header. With such a flag,reception apparatus 20 may determine that the head TLV packet is a TLVpacket with reference clock information.

In addition, the identifier (information) indicating that the TLV packetis a TLV packet with reference clock information may be stored in theTMCC control information. FIG. 16 is a diagram illustrating structure ofthe TMCC control information under a transfer scheme for advancedbroadband satellite digital broadcast.

The information for specifying and referencing the TLV packet withreference clock information may be stored in extension informationwithin the TMCC control information illustrated in FIG. 16 , and may bestored in another place within the TMCC control information. Forexample, stream classification/relative stream information in the TMCCcontrol information may be used as information for specifying andreferencing the TLV packet with reference clock information. FIG. 17 isa diagram illustrating the stream classification/relative streaminformation in the TMCC control information.

In FIG. 17 , in the stream classification/relative stream information,the stream classification of each of 16 streams is indicated in 8 bits.That is, 1-frame transfer slot can transfer up to 16 (16-classification)streams. For example, the stream classification of an MPEG2-TS stream is“00000000”, and the stream classification of a TLV stream is “00000010”.However, under the current circumstances, the classifications of otherstreams are unassigned or undefined.

Therefore, when the stream classification of the TLV stream withreference clock is defined, for example, as “00000100” and the relativestream is a TLV stream with a reference clock, “00000100” is stored inthe stream classification/relative stream information in the TMCCcontrol information. Here, in the stream with the stream classificationof “00000100”, the TLV packet containing reference clock information isstored, for example, once per 5-slot unit which is a slot assignmentunit, or once per frame unit.

Reception apparatus 20 analyzes the stream classification/relativestream information in the TMCC control information. When the streamclassification is “00000100”, reception apparatus 20 acquires the TLVpacket with reference clock information from the slot determined inadvance.

Note that a case may be considered where the stream classificationincluding download type TLV packets and the stream classificationincluding stream type TLV packets, such as video and audio, are defined.In such a case, reception apparatus 20 may determine that the referenceclock information is contained in the stream when the streamclassification of the received stream is a stream type TLV packet. Thisis because the reference clock information is not used in reproductionof download type TLV packets.

In addition, when the information for specifying and referencing the TLVpacket with reference clock information is stored in the extensioninformation of the TMCC control information, for example, informationfor each of the 16 relative streams is stored in the extension area ofthe TMCC control information.

Also, as illustrated in FIG. 18 , an area into which the reference clockinformation is stored may be newly defined in the undefined field of theslot header. FIG. 18 is a diagram illustrating an example in which thereference clock information is stored in the undefined field of the slotheader.

Also, the reference clock information may be stored in a previouslydetermined slot, and information indicating that the reference clockinformation is contained may be stored within the slot header. Here, thepreviously determined slot is, for example, a head slot of the transferslot (Slot #1 in the example of FIG. 13 ), and the reference clockinformation stored in the IP packet may be contained in the head TLVpacket within this slot.

Also, when the plurality of streams are contained in the transfer slot,the previously determined slot may be, for example, a head slot of eachstream contained in the transfer slot, and the reference clockinformation stored in the IP packet may be contained in the head TLVpacket within this slot.

Also, the TMCC control information may store information for specifyingand referencing the slot header containing the reference clockinformation. Note that the storage method of the information forspecifying and referencing the slot header containing reference clockinformation in the TMCC control information is similar to theaforementioned storage method of the information for specifying andreferencing the TLV packet with reference clock information, and thusdescription thereof will be omitted.

Reception apparatus 20 analyzes the TMCC control information, and whendetermination is made that the reference clock information is in theslot header, reception apparatus 20 extracts the reference clockinformation from the slot header.

Also, the TMCC control information may store information indicating thatthe reference clock information is contained. FIG. 19 is a block diagramillustrating a functional configuration of reception apparatus 20 whenthe information indicating that the reference clock information iscontained within the slot header is stored in the TMCC controlinformation. FIG. 20 is an acquisition flow of the reference clockinformation when the information indicating that the reference clockinformation is contained in the slot header is stored in the TMCCcontrol information.

In FIG. 19 , when the information indicating that the reference clockinformation is contained within the slot header is stored in the TMCCcontrol information, in reception apparatus 20, reference clockinformation extractor 15 acquires the reference clock information fromthe transfer slot that is output from decoder 11.

In the flow of FIG. 20 , decoder 11 decodes the transfer channel codeddata (S131), analyzes the TMCC control information (S132), anddetermines whether the reference clock information is in the slot headerwithin the transfer slot (S133). When the reference clock information isin the slot header (Yes in S133), reference clock information extractor15 extracts the reference clock information from the slot header (S134),and reference clock generator 16 generates the reference clock of thesystem (system clock) based on the reference clock information (S135).On the other hand, when the reference clock information is not in theslot header (No in S133), the acquisition flow of the reference clockinformation ends.

Reception apparatus 20, which can acquire the reference clockinformation in the layer of the transfer slot, can acquire the referenceclock information more quickly than a case where the reference clockinformation is stored in the TLV packet.

As described above, by storing the reference clock information in theTLV packet or transfer slot, reception apparatus 20 can reduce theprocesses until the acquisition of the reference clock information, andmay shorten acquisition time of the reference clock information.

In addition, by storing the reference clock information in a physicallayer, reception apparatus 20 can easily implement acquisition andreproduction of the reference clock information by hardware, and clockreproduction with higher-precision is possible than acquisition andreproduction of the reference clock information by software.

In addition, in the aforementioned transmission method according to thefirst exemplary embodiment, in the system in which the plurality oflayers (protocols) exists including the IP layer, the transmissionapparatus adds the time stamp of a medium based on the reference clockinformation in the layers upper than the IP layer, and transmits thereference clock information in the layers lower than the IP layer. Thisallows reception apparatus 20 to easily process the reference clockinformation by hardware.

Note that, based on a similar idea, storing the reference clockinformation in a condition of not being stored in the MMT packet withinthe IP packet can also be considered. Even in such a case, receptionapparatus 20 can reduce the processes for acquiring the reference clockinformation as compared with the case where the reference clockinformation is stored in the MMT packet.

[Transmission Cycle of the Reference Clock Information]

A transmission cycle of the reference clock information will besupplemented below.

In the case of storing the reference clock information in the TLVpacket, for example, the transmission apparatus stores time when thehead bit of the TLV packet is transmitted as the reference clockinformation. In addition, not the transmission time of the head bit butpredetermined time determined differently may be stored as the referenceclock information.

The TLV packet containing the reference clock information is transmittedat predetermined intervals. In other words, the TLV packet containingthe reference clock information is contained in the transfer slot and istransmitted in a predetermined transmission cycle. For example, at leastone or more pieces of the reference clock information may be stored inthe TLV packets and be transferred at intervals of 100 ms.

In addition, the transmission apparatus may dispose the TLV packets thatcontain the reference clock information at predetermined intervals atpredetermined positions of the transfer slot under the advanced BStransfer scheme. In addition, the transmission apparatus may store theTLV packet containing the reference clock information once every 5-slotunit which is a slot assignment unit of the TLV packet, and may storethe reference clock information in the head TLV packet of the first slotof the 5-slot unit. That is, the transmission apparatus may dispose theTLV packet that contains the reference clock information at a headwithin the head slot within the transfer slot (that is, immediatelyafter the slot header).

In addition, the transmission apparatus may dispose the TLV packets thatcontain the reference clock information at predetermined intervals atpredetermined positions of the transfer slot under the transfer schemefor advanced broadband satellite digital broadcast. For example, thetransmission apparatus may store the reference clock information onceevery 5-slot unit which is a slot assignment unit in the head TLV packetof the first slot. That is, the TLV packet positioned at a head withinthe head slot of each stream contained in the transfer slot may containthe reference clock information. Also, the reference clock informationmay be stored in the first slot within the relative stream.

In addition, the transmission cycle and transmission interval of thereference clock information may be changed according to a modulationscheme or coding rate of the transfer channel coding scheme.

[Method for acquiring the reference clock information in the upper layerquickly] Next, a method will be described for shortening time to theacquisition of the reference clock information by reception apparatus 20performing batch DEMUX processing from the lower layer to the upperlayer.

Here, a method will be described by which the transmission apparatusstores the reference clock information in the upper layer such as theMMT packet, and stores in the IP packet the MMT packet in which thereference clock information is stored. In the method described below, bydefining a protocol for storing in the TLV packet the IP packet in whichthe reference clock information is stored, the reception apparatus makesa direct reference to the MMT packet, which is the upper layer, from thelower layer such as the TLV packet, and acquires the reference clockinformation contained in the MMT packet without performance of normalDEMUX processing.

The transmission apparatus contains the reference clock information inthe aforementioned control information stored in the MMT packet. Thepreviously determined packet ID is added to the control informationcontaining the reference clock information. Then, the transmissionapparatus stores the MMT packet containing the reference clockinformation in a dedicated IP data flow, and adds the previouslydetermined source IP address, destination IP address, source portnumber, destination port number, and protocol classification.

On receipt of the transfer channel coded data generated in this way,reception apparatus 20 may extract the IP packet containing thereference clock information by TLV demultiplexer 12 acquiring thepreviously determined IP data flow.

Note that, when the IP packet undergoes header compression processing,the reception apparatus adds, for example, an identifier indicating thatthe IP packet contains the reference clock information to a contextidentifier indicating identical IP data flow. The context identifier isstored in a compressed IP packet header. In this case, receptionapparatus 20 can extract the IP packet containing the reference clockinformation with reference to the context identifier in the compressedIP packet header.

In addition, the IP packet containing the reference clock informationmay be prescribed not to undergo the header compression, and may beprescribed to always undergo the header compression. It may beprescribed that the previously determined context identifier is added tothe IP packet containing the reference clock information, and that allthe headers are compressed.

In addition, a method may also be considered for defining, in a TLV datatype field, an identifier indicating that the TLV packet is an IP packetthat belongs to the IP data flow containing the reference clockinformation, or an identifier indicating that the TLV packet is acompressed IP packet that belongs to the IP data flow containing thereference clock information. Also, such an identifier may be defined ina field other than the TLV data type field.

When a direct reference to the reference clock information is made fromthe lower layer, the reference clock information is stored at apreviously determined position, and packets in which the reference clockinformation is stored (such as the MMT packet, IP packet, and TLVpacket) are packets dedicated to the reference clock information. Inaddition, a length of the field before the reference clock informationbecomes fixed by a packet header length being fixed.

However, the length of the field before the reference clock informationdoes not need to be fixed. The reception apparatus only needs to specifythe length of the field before the reference clock information in thelower layer. For example, when information on the length to thereference clock information includes two types, A and B, receptionapparatus 20 can specify the position of the reference clock informationby signaling which of A and B the length information is in the lowerlayer. Alternatively, by the transmission apparatus storing in the lowerlayer positional information on the reference clock information thatallows a direct reference to the reference clock information in theupper layer, reception apparatus 20 may make a reference from the lowerlayer based on the positional information.

The following describes a specific method for shortening acquisitiontime of the reference clock information in the upper layer.

Reception apparatus 20 determines the TLV data type. On determinationthat the reference clock information is contained, reception apparatus20 acquires the reference clock information contained within the MMTpacket directly from the IP packet.

Reception apparatus 20 may extract the reference clock informationcontained in the MMT packet by extracting a bit string at a specificposition from the IP packet or compressed IP packet, with analysis ofthe IP address, port number, or context identifier omitted. “Extractinga bit string at a specific position” means, for example, extractinginformation of a specific length from a position that is offset byfixed-length bytes from the TLV packet header. The reference clockinformation is acquired by “extracting a bit string at a specificposition”.

The offset length of the fixed-length bytes for extracting the referenceclock information is uniquely determined for each of the IP packet andthe compressed IP packet. Therefore, reception apparatus 20 can acquirethe reference clock information by extracting the information of thespecific length from the position that is offset by the fixed-lengthbytes immediately after determining the TLV data type. Note that theextraction of the information may be performed not from the positionthat is offset by the fixed length from the TLV packet header but from aposition that is offset by the fixed length from a specific field ofTLV.

Note that the aforementioned method is one example, and the referenceclock information in the upper layer may be acquired from the lowerlayer through definition of another protocol or identifier. For example,an identifier indicating whether the IP packet contains the referenceclock information may be stored in a field other than the TLV data typefield.

In addition, for example, reception apparatus 20 may extract referencetime information contained in the MMT packet by extracting the bitstring at a specific position from the IP packet or compressed IP packetwhile omitting to analyze the IP address, the port number, and thecontext identifier.

When it is difficult to determine the IP data flow containing thereference clock information from identification information on the IPdata flow, reception apparatus 20 may specify the MMT packet containingthe reference clock information based on unique identificationinformation (packet ID) added to the MMT packet containing the referenceclock information. In this case, the reference clock information isextracted from the specific field as described above.

Also, when the reference clock information contained in the MMT packetis not stored at the position determined in advance or when the positionwhere the reference clock information contained in the MMT packet isstored cannot be specified, reception apparatus 20 specifies the MMTpacket containing the reference clock information by using theaforementioned method, specifies the position of the reference clockinformation based on MMT packet header information, and extracts thereference clock information.

Note that, although an example has been described above in which the MMTpacket is stored in the IP packet, data to be stored in the IP packetdoes not need to be the MMT packet, but may be, for example, data thathas another data structure. That is, the reference clock information maybe contained in the IP packet in data structure different from datastructure of the MMT packet. Even for data with different datastructure, in a similar manner to the aforementioned example, datacontaining the reference clock information is stored in a dedicated IPdata flow, and identification information indicating that the datacontains the reference clock information and identification informationindicating that the data is an IP data flow containing the referenceclock information are added.

Reception apparatus 20 identifies that the data is data containing thereference clock information, or that the data is an IP data flowcontaining data containing the reference clock information. When thereference clock information is contained, reception apparatus 20extracts the reference clock information. Also, when the reference clockinformation is stored at a specific position of data, receptionapparatus can extract the reference clock information contained in thedata with reference to the specific position from packet structure ofthe lower layer.

In the aforementioned example, in order to extract the reference clockinformation from the IP packet or the compressed IP packet, based onwhether the data is the IP packet or the compressed IP packet, receptionapparatus 20 extracts the reference clock information from respectivefixed-length offset positions different from each other. However, if itis predetermined that header compression processing is omitted on the IPpacket containing the reference clock information, or if it ispredetermined that all the IP packets containing the reference clockinformation undergo header compression, reception apparatus 20 may omitthe determination whether the data is the IP packet or the compressed IPpacket. Also, reception apparatus 20 may perform determination whetherthe reference clock information is contained, after the header of thecompressed IP packet is decompressed.

A reception method for extracting the bit string at a specific positionfrom the IP packet or compressed IP packet will be described below withreference to the flowchart. FIG. 21 is a flowchart for extracting thebit string at a specific position from the IP packet or compressed IPpacket. Note that the configuration of reception apparatus 20 is similarto the block diagram illustrated in FIG. 8 .

In the flow of FIG. 21 , first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S141), and extracts the TLV packetfrom the transfer channel slot (S142).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S143),and determines whether the data type is an IP containing reference clockinformation (S144). When the determination is made that the data type isnot an IP packet containing reference clock information (No in S144),the flow ends. When the determination is made that the data type is anIP packet containing reference clock information (Yes in S144), TLVdemultiplexer 12 determines whether the IP header is compressed (S145).

When the IP header is not compressed (No in S145), reference clockinformation extractor 15 acquires the reference clock informationcontained within the MMT packet at a position that is offset byfixed-length N bytes from the TLV header (S146). When the IP header iscompressed (Yes in S145), reference clock information extractor 15acquires the reference clock information contained within the MMT packetat a position that is offset by fixed-length M bytes from the TLV header(S147).

For example, when the determination is made in step S145 that the IPheader undergoes compression processing, in step S146, reference clockinformation extractor 15 acquires the reference clock informationcontained in the MMT packet from the position that is offset by N bytesfrom the TLV header. On the other hand, when the determination is madein step S145 that the IP header does not undergo compression processing,in step S147, reference clock information extractor 15 acquires thereference clock information contained in the MMT packet from theposition that is offset by M bytes from the TLV header.

Finally, reference clock generator 16 generates the system clock basedon the reference clock information (S148).

Note that, since data structure of the IP packet header differsaccording to whether the IP packet is IPv4 or IPv6, the fixed-length Nbytes and M bytes have different values.

While the normal MMT packet containing audio, video, control signal, andthe like undergoes DEMUX processing in normal steps, the MMT packetcontaining the reference clock information undergoes batch DEMUXprocessing from the lower layer to the upper layer. This allows thereception apparatus to acquire the reference clock information in thelower layer even when the reference clock information is stored in theupper layer. That is, the reception apparatus can reduce the processesfor acquisition of the reference clock information, shorten time to theacquisition of the reference clock information, and facilitate hardwareimplementation.

Second Exemplary Embodiment

Currently, as a method for using an extension area in TMCC controlinformation (hereinafter also simply referred to as TMCC) under anadvanced BS transfer scheme, ARIB (Association of Radio Industries andBusinesses) is studying a method for transmitting urgent information andthe like as a payload.

However, a proposed conventional method for using the extension area inthe TMCC control information is limited to a method for transmitting adata payload, such as text and images, by using the TMCC controlinformation extending over several frames. Therefore, the method forusing the extension area in the TMCC control information will belimited, which needs to be addressed.

For example, it is difficult to store control information (controlsignal) that does not change in value for each frame, such as aconventional transfer mode and slot information, or control informationthat changes in value for each frame such as reference clockinformation, in the extension area of the TMCC control informationsimultaneously with payload data extending over several frames.

Therefore, the second exemplary embodiment describes a method for makingit possible to store data with different reception processingsimultaneously in the extension area of the TMCC control information, bydividing the extension area of the TMCC control information inaccordance with a classification of information and data to be stored inthe extension area of the TMCC control information. The presentdisclosure can enhance flexibility of extension by providingextensibility to the use of the extension area. Also, the receptionapparatus can perform reception and analysis of the TMCC controlinformation by reception methods different for each classification basedon the classification of data.

In addition, the method according to the present disclosure allowspayload data extending over several frames and payload data of one frameto be included together in the extension area. Since the receptionapparatus can acquire the payload data of one frame first even while thepayload data extending over several frames cannot be received, urgentinformation can be acquired and presented more quickly.

[Structure of TMCC Extension Information]

Structure of TMCC extension information will be described below. Notethat basic structure of the TMCC control information is structureillustrated in FIG. 16 . The control information to be stored in theTMCC control information is classified roughly into a first type and asecond type below.

The first type of control information relates to frames, and does notchange in value for each frame. A minimum update interval of the controlinformation that does not change in value for each frame is a frameunit. Here, when the value of the control information is changed,control information after the change is transmitted two frames ahead.Also, when the value of the control information is changed, notificationis made by increment of an 8-bit change instruction. Specifically,information other than pointer information and slot informationcorresponds to the control information that does not change in value foreach frame.

The second type of control information relates to frames, and changes invalue for each frame. Since the control information that changes invalue for each frame is information that changes in value for eachframe, the change instruction is not made. Specifically, the controlinformation that changes in value for each frame is the pointerinformation and the slot information.

FIG. 22A is a diagram illustrating structure of the TMCC extensioninformation. In FIG. 22A, the TMCC extension information includes 16-bitextension identification and 3598-bit extension area. Setting a valueother than all 0 in the extension identification validates the extensionarea.

FIG. 22B is a diagram illustrating an example of a conventionallyproposed bit assignment method when the extension area is used as apayload. In FIG. 22 (b), when the extension area is used as a payload, anumber of pages includes 16 bits, and indicates over how many frames ofthe TMCC control information during transfer an additional informationpayload is transferred.

A page number includes 16 bits, and indicates in which page the TMCCcontrol information during transfer is among the number of pages. Anadditional information classification includes 8 bits, and specifies theclassification of the additional information. Specifically, theadditional information classification is, for example, superimposedcharacters (subtitles), graphics, audio, and the like.

All of the extension area will be used as a payload, and it is difficultto store control information such as the conventional TMCC controlinformation.

[Extension Method of the TMCC Extension Area]

Here, a method will be described for storing data with differentreception processing in the TMCC extension area, by dividing the TMCCextension area in accordance with the classification of information anddata to be stored in the TMCC extension area.

The classification of information and data to be stored in the TMCCextension area (hereinafter referred to as an extension classification)is classified as follows, for example.

Type A:

-   -   Type A indicates control information that relates to frames and        does not change in value for each frame.    -   Minimum update interval is a frame unit. When there is a change        in the value, information after the change is transmitted two        frames ahead.    -   When there is a change in the value, notification of the change        is made by increment of the 8-bit change instruction.        Type B:    -   Type B indicates control information that relates to frames and        changes in value for each frame.    -   Type B indicates information that changes in value for each        frame, and the change instruction is not made.        Type C:    -   Type C indicates information or data that is used as a payload        (conventional extension scheme).    -   However, for the change instruction, a change instruction field        which is identical to TMCC which is not the extension area may        be used, and the change instruction field may be independently        prescribed in the extension area.

FIG. 23 is a diagram illustrating an example of data structure (bitarrangement) of the extension area where the classified extensionclassification is used. FIG. 24A is a diagram illustrating an example ofsyntax when the extension classification is used. FIG. 24B is a diagramillustrating another example of syntax when the extension classificationis used.

In FIG. 23 , the aforementioned three types are defined as the extensionclassification. In addition, in FIG. 24A, subsequently to storage of adata length in each of the three types of extension classification,extension data with a length indicated in the data length is stored foreach extension classification. The reception apparatus extracts datawith the length indicated in the data length from the extension area foreach extension classification, and performs processing.

For example, regarding data of Type A, the reception apparatus acquiresthe data when there is a change instruction. When there is a change inthe data of Type A, the reception apparatus considers that the controlinformation is changed, and performs processing on the controlinformation in accordance with the change.

Also, regarding data of Type B, since the data of Type B changes invalue for each frame, the reception apparatus acquires the data forevery frame. For example, when the reference clock information thatchanges in value for each frame is stored in the TMCC controlinformation, the reference clock information is stored in a data area ofType B.

Data of Type C contains payload information of the conventionalextension scheme. Regarding the data of Type C, the reception apparatusperforms operation in accordance with acquisition under the conventionalextension scheme.

In the aforementioned example, details of data structure for eachextension classification are separately prescribed. When prescribedseparately, an identifier similar to the additional informationclassification and an object service specification method in the data ofType C in FIG. 22 (b) may be prescribed in other types. Note that theadditional information classification may be defined using a commontable, and the extension identification and the additional informationclassification may be merged.

In addition, information that may change in data length on the way maybe considered as a classification similar to the data of Type A. Whenthere is a change in the data length, a change instruction may be madethrough transmission of information after the change two frames ahead.When there is a change instruction, the reception apparatus confirmswhether there is any change in the data length with reference to thedata length of the extension classification.

Note that the data structure is not limited to the structure asillustrated in FIG. 23 . For example, when the data length of theextension classification is fixed in advance, transmission of the datalength may be omitted. Specifically, when the data length with theextension classification of Type A is fixed-length in FIG. 23 ,disposition of the data length with the extension classification of TypeA may be omitted within the data structure. In addition, when the datalength with the extension classification of Type A and the data lengthwith the extension classification of Type B are fixed-length,disposition of the data length of all types may be omitted. In addition,a flag that indicates whether there is any data of the extensionclassification may be provided within the data structure.

In addition, syntax for using the extension classification is notlimited to syntax illustrated in FIG. 24A. For example, in FIG. 24B, anextension area number is set, and the extension classification andextension area length are stored for each extension area number in thesyntax. Subsequently, the extension data of the extension area number isstored in the syntax.

The syntax in FIG. 24A and FIG. 24B may support addition of theextension classification in the future. In addition, since the syntax inFIG. 24 and FIG. 24B enables storage of a plurality of pieces of datawith identical extension classification, it is not necessary todetermine details of data structure for each identical extensionclassification in advance. In addition, even when used as a payload (asType C), the syntax in FIG. 24 and FIG. 24B allows description of aplurality of pieces of data with different number of pages, such asvideo and audio, in an identical frame.

Note that, in the syntax of FIG. 24B, the extension area number,extension classification, and extension area length may beclassifications similar to Type A. That is, these pieces of informationmay be prescribed to be information that follows the change instruction.Therefore, the reception apparatus can easily make a determination onpresence of changes by continuous storage of data that follows thechange instruction.

In addition, an undefined area may be provided in the extensionclassification in preparation for future extension. As an extensionclassification to be introduced in the future, for example, thefollowing classifications are assumed.

-   -   This is a control signal to be updated for each several frames,        and the change instruction is not made.    -   For an urgent signal, the change instruction is made in a        similar manner to Type A. However, processing of value change is        performed in the frame immediately after acquisition of the        change instruction, instead of after acquisition of information        that is two frames ahead.

Also, for the aforementioned urgent signal, an urgent flag may betransmitted using the extension classification accompanied by the changeinstruction, and urgent data may be transmitted using a payload. Also,the extension classification may be classified in accordance withwhether to follow the change instruction.

[Detailed Structure and Operation Flow]

A functional configuration and operation flow of the reception apparatusas described above will be described. FIG. 25 is a block diagramillustrating the functional configuration of the reception apparatusaccording to the second exemplary embodiment. FIG. 26 is a diagramillustrating the operation flow of the reception apparatus according tothe second exemplary embodiment. Note that, in the followingdescription, the extension classification includes three types, Type A,Type B, and Type C, as described above.

As illustrated in FIG. 25 , reception apparatus 40 includes extensionidentifier 41, extension classification determiner 42, changeinstruction checker 43, data update checker 44, and update data acquirer45.

First, extension identifier 41 analyzes the extension identification ofthe TMCC control information (S161). When the extension identificationis other than all 0 here, extension identifier 41 considers that theextension area is effective, and reception apparatus 40 executes thefollowing processing for each extension area.

Next, extension classification determiner 42 discriminates (determines)the extension classification (S162). When it is discriminated that theextension classification is Type A (Type A in S162), data of an areaspecified by an extension area length is control information which doesnot change in value for each frame, the control information following achange instruction. Therefore, change instruction checker 43 checks thechange instruction for each frame (S163).

Subsequently, data update checker 44 determines data update (S164). Whenit is determined that there is a change instruction and that there is achange in the extension data (Yes in S164), update data acquirer 45acquires updated extension data and executes processing accompanying thechange (S165).

On the other hand, when it is not determined as described above in stepS164 (No in S164), update data acquirer 45 determines that there is nochange in the extension data.

Also, when it is discriminated in step S162 that the extensionclassification is Type B (Type B in S162), update data acquirer 45references data specified by the extension area length, acquires dataupdated for each frame, and executes processing accompanying the change(S167).

When it is discriminated in step S162 that the extension classificationis Type C (Type C in S162), update data acquirer 45 executes processingbased on the conventional reception method under the payload extensionscheme (S166).

Note that, when it is discriminated that the extension area number,extension classification, and extension area length are classificationssimilar to Type A that follows the change instruction as describedabove, update data acquirer 45 checks change instructions. When there isa change instruction, update data acquirer 45 checks whether informationis updated.

Note that reception apparatus 40 may determine reception processingbased on the extension classification, and may determine in whichprocessing block the data processing should be performed. Receptionapparatus 40 may determine, for example, to process the data of Type Aand the data of Type B by hardware, and to process the data of Type C bysoftware.

[Advantageous Effects, Etc.]

As described above, the second exemplary embodiment has described themethod for dividing the TMCC extension area under the advanced BStransfer scheme for each extension classification, and for storing theextension data in the TMCC extension area. Reception apparatus 40determines the extension data processing method based on the extensionclassification.

This makes it possible to store a plurality of pieces of data withdifferent reception processing in the TMCC extension areasimultaneously. That is, the present disclosure makes it possible toprovide extensibility to the method for using the TMCC extension area.

Specifically, for example, the present disclosure makes it possible tostore the payload and the reference clock information in the TMCCextension area simultaneously.

Also, it is possible to cause the payload data extending over severalframes and the payload data of one frame to be included together in theTMCC extension area. Therefore, even when it is difficult to receive thepayload data extending over several frames, reception apparatus 40 canfirst acquire the payload data of one frame. Therefore, receptionapparatus 40 can acquire and present urgent information more quickly.

Other Exemplary Embodiments

Although the exemplary embodiments have been described above, thepresent disclosure is not limited to the aforementioned exemplaryembodiments.

Although the storage method of the reference clock information has beendescribed in the aforementioned exemplary embodiments, a plurality ofpieces of reference clock information may be transmitted in one or morelayers. When the plurality of pieces of reference clock information istransmitted, reception apparatus 20 may select one piece of thereference clock information and use the selected reference clockinformation for generation of the reference clock (system clock), andmay use both pieces of the reference clock information to generate thereference clock. Reception apparatus 20 may select high-precisionreference clock information, and may select reference clock informationthat may be acquired more quickly.

Also, when the reference clock information is transmitted in a pluralityof layers, the transmission apparatus may store information indicatingthat the reference clock information is transmitted in the plurality oflayers. In addition, the information indicating that the reference clockinformation is transmitted in the plurality of layers, or informationrelated to the layers or protocols in which the reference clockinformation is transmitted may be transmitted in the lower layer.

This allows reception apparatus 20 to determine that the reference clockinformation is contained in the upper layer during DEMUX processing inthe lower layer, and to determine which reference clock information touse based on this determination. Reception apparatus 20 may determinewhich reference clock information to use based on which layer ofreference clock reproduction is supported, and reception apparatus 20may use reference clock reproduction recommended by broadcasting stationapparatuses.

When the reference clock information is transmitted in the plurality oflayers, reception apparatus 20 may extract the reference clockinformation in the lower layer, and may further extract the referenceclock information contained in the layers from the lower layer to theupper layer. Then, reception apparatus 20 may use at least one or morepieces of the extracted reference clock information to generate thereference clock.

In addition, the plurality of pieces of reference clock information maybe transmitted through a plurality of transfer channels. In this case,information indicating that the plurality of pieces of reference clockinformation is transmitted through the plurality of transfer channels,and information related to the transfer channels through which thereference clock information is transferred may be transmitted.

Also, for example, in addition to a conventional 32-bit short-format NTPcontained in the MMT packet header, when higher-precision referenceclock information is transmitted, the transmission apparatus furthertransmits information for allowing reception apparatus 20 to use thehigh-precision reference clock information to reproduce the 32-bitshort-format NTP. Such information is, for example, time informationindicating a relative relationship between clocks, and is transmitted byusing CRI_descriptor( ), etc.

Note that, when reception apparatus 20 can reproduce the 32-bitshort-format NTP, the conventional NTP field contained in the MMT packetheader is unnecessary. Therefore, the transmission apparatus may storeanother piece of information in the NTP field, and may perform headercompression processing by reducing the NTP field. When the headercompression processing is performed, the transmission apparatustransmits information indicating that the NTP field is reduced. When theNTP field is reduced, reception apparatus 20 generates the referenceclock by using another piece of reference clock information, andreproduces the 32-bit short-format NTP.

In addition, when the MMT packet is transferred using a broadbandchannel, a broadband reception apparatus may use not the reference clockinformation but the 32-bit short-format NTP for QoS control.Accordingly, a broadband transmission apparatus may omit to transmit thereference clock information through the broadband channel. In addition,when end-to-end delay of the broadband channel is within a certainvalue, the broadband reception apparatus may use the reference clockinformation for clock reproduction.

Note that although the aforementioned first exemplary embodiment hasdescribed the case where the MMT/IP/TLV scheme is used as an example,schemes other than the MMT scheme may be used as a multiplexing scheme.For example, the present disclosure may be applied to an MPEG2-TSscheme, RTP scheme, or MPEG-DASH scheme.

In addition, methods for header compression of IP packets include RoHC(Robust Header Compression) and HCfB (Header Compression forBroadcasting).

Schemes for storing IP packets in broadcast include a GSE (GenericStream Encapsulation) scheme, IPoverTS scheme using ULE (UnidirectionalLight-weight. Encapsulation), and the like, in addition to the TLVscheme.

The present disclosure may be applied to a case where any of suchschemes is used. Application of the present disclosure allows receptionapparatus 20 to achieve shortening of time to the acquisition of thereference clock information and reduction in the processes, and toachieve high precision of the clock by hardware implementation.

Note that, while the reference clock information in the aforementionedexemplary embodiments is NTP when the multiplexing scheme is MMT, forexample, when the multiplexing scheme is an MPEG2-TS scheme, thereference clock information is PCR (Program Clock Reference). Also, asthe reference clock information, even when the multiplexing scheme isMMT, PTP prescribed by IEEE (Institute of Electrical and ElectronicsEngineers) 1588 may be transferred in an NTP form, and only some bits ofNTP may be transferred. That is, the reference clock information onlyneeds to be information indicating time that is set by the transmissionapparatus. Note that NTP does not necessarily mean an NTP value in anNTP server commonly used on the Internet.

In addition, the present disclosure may be implemented as a transmissionapparatus (transmission method) that transmits the transfer slot thatstores the reference clock information by the above method. Thefollowing supplements a configuration of the transmission apparatus.FIG. 27 is a block diagram illustrating a functional configuration ofthe transmission apparatus. FIG. 28 is an operation flow of thetransmission apparatus.

In FIG. 27 , transmission apparatus 30 includes generator 31 andtransmitter 32. Note that each component of transmission apparatus 30 isspecifically implemented by a microcomputer, a processor, a dedicatedcircuit, or the like.

Transmission apparatus 30 is specifically a broadcasting server, and isan example of the aforementioned “transmission apparatus” of the firstexemplary embodiment.

Generator 31 generates, for example, the transfer slot that stores theplurality of slots that each store one or more TLV packets that eachstore the IP packet (S151 of FIG. 28 ). For example, a plurality ofrelative streams that each include one or more slots is contained in thetransfer slot.

Generator 31 contains the reference clock information, such as the NTPthat indicates time for reproduction of content (for example, broadcastcontent such as video or audio), in the IP packet stored in the TLVpacket positioned at a head within the head slot within the transferslot (hereinafter this IP packet is also referred to as an object IPpacket). That is, generator 31 contains the reference clock informationin the IP packet stored in the TLV packet positioned at a head withinthe transfer slot. The object IP packet is an IP packet that does notundergo header compression processing, and the reference clockinformation is stored, for example, within the object IP packet in datastructure different from data structure of the MMT packet.

Specifically, generator 31 includes a coder that codes the broadcastcontent, MMT multiplexer, IP multiplexer, TLV multiplexer, and the like.Here, the TLV packet is an example of a first transfer unit, the slot isan example of a second transfer unit, and the transfer slot is anexample of a transfer frame. The relative stream is an example of thestream.

Transmitter 32 transmits the transfer slot generated by generator 31(transfer channel coded data containing the transfer slot) throughbroadcast (S152 of FIG. 28 ).

As also described in the aforementioned first exemplary embodiment,transmission apparatus 30 can simplify the processes by which receptionapparatus 20 acquires the reference clock information of each of theplurality of streams. Therefore, reception apparatus 20 can shorten timeuntil reception apparatus 20 acquires the reference clock information.

Note that in the aforementioned exemplary embodiments, components mayeach include dedicated hardware or may be implemented through executionof a software program suitable for each component. The components may beeach implemented by a program execution unit, such as a CPU and aprocessor, reading and executing the software program recorded in arecording medium such as a hard disk and a semiconductor memory.

In addition, the components may be circuits. These circuits mayconstitute one circuit as a whole, and may be different circuits. Inaddition, each of these circuits may be a general-purpose circuit, andmay be a dedicated circuit.

For example, in each of the aforementioned exemplary embodiments,processes executed by a specific processor may be executed by anotherprocessor. In addition, order of the plurality of processes may bechanged, and the plurality of processes may be executed in parallel.

The reception apparatus (reception method) and transmission apparatus(transmission method) according to one or more aspects have beendescribed above based on the exemplary embodiments. However, the presentdisclosure is not limited to these exemplary embodiments. The presentexemplary embodiments to which various modifications conceivable by aperson skilled in the art are made, and aspects that are made bycombining elements of different exemplary embodiments may also be withinthe scope of the one or more aspects as long as such aspects do notdepart from the gist of the present disclosure.

The transmission method according to the present disclosure is useful asa transmission method capable of reducing the processes of the receptionapparatus for acquiring the reference clock information when the MMTscheme is applied to a broadcasting system.

What is claimed is:
 1. A transmission method, comprising: generatingframes, each frame including first control data, second control data,and a first transfer unit, the first transfer unit includes one or moresecond transfer units, the first control data including firstinformation indicating a start position of the one or more secondtransfer units within the first transfer unit, the second control dataincluding second information indicating whether the first control dataincludes reference clock information or not, the first control dataincluding the reference clock information when the second informationindicates the first control data includes the reference clockinformation; and transmitting the frames, wherein the reference clockinformation is cyclically transmitted, (i) a first frame among theframes includes the first control data including the reference clockinformation and the second control data indicating that the firstcontrol information includes the reference clock information, and (ii) asecond frame among the frames includes the first control data notincluding the reference clock information and the second control dataindicating that the first control data does not include the referenceclock information, and the reference clock information is based onPrecision Time Protocol (PTP) prescribed by Institute of Electrical andElectronics Engineers (IEEE)
 1588. 2. The transmission method to claim1, wherein the first transfer unit has a fixed-length, and each of theone or more second transfer units has a variable length.
 3. Thetransmission method according to claim 1, wherein the first transferunit is a slot, each of the one or more second transfer units is a TypeLength Value (TLV) packet, the first control data is transmitted in aslot header, and the second control data is transmitted in aTransmission and Multiplexing Configuration Control (TMCC) signal. 4.The transmission method according to claim 1, wherein the referenceclock information includes a current clock value used at a receiver toreproduce a reference clock signal.
 5. A transmission apparatus,comprising: a frame configurator that, in operation, generates frames,each frame including first control data, second control data, and afirst transfer unit, the first transfer unit includes one or more secondtransfer units, the first control data including first informationindicating a start position of the one or more second transfer unitswithin the first transfer unit, the second control data including secondinformation indicating whether the first control data includes referenceclock information or not, the first control data including the referenceclock information when the second information indicates the firstcontrol data includes the reference clock information; and a transmitterthat, in operation, transmits the frames, wherein the reference clockinformation is cyclically transmitted, (i) a first frame among theframes includes the first control data including the reference clockinformation and the second control data indicating that the firstcontrol information includes the reference clock information, and (ii) asecond frame among the frames includes the first control data notincluding the reference clock information and the second control dataindicating that the first control data does not include the referenceclock information, and the reference clock information is based onPrecision Time Protocol (PTP) prescribed by Institute of Electrical andElectronics Engineers (IEEE)
 1588. 6. The transmission apparatusaccording to claim 5, wherein the first transfer unit has afixed-length, and each of the one or more second transfer units has avariable length.
 7. The transmission apparatus according to claim 5,wherein the first transfer unit is a slot, each of the second transferunits is a Type Length Value (TLV) packet, the first control data istransmitted in a slot header, and the second control data is transmittedin a Transmission and Multiplexing Configuration Control (TMCC) signal.8. The transmission apparatus according to claim 5, wherein thereference clock information includes a current clock value used at areceiver to reproduce a reference clock signal.